1. Technical Field
The present invention relates to a trigger switch used in an electric tool and the like.
2. Related Art
Conventionally, for example, Japanese Patent Publication No. 6-18092 proposes that a seal material is bonded to a case of which micro-grooves are provided in a surface so as to prevent an adverse effect of expansion of air and an adverse effect of dust and the like on a switch. However, when the dust-resistant structure proposed in Japanese Patent Publication No. 6-18092 is applied to the trigger switch, the dust and water invade easily into the trigger switch from the micro-grooves by pumping action caused by a manipulation of a trigger, which possibly causes the adverse effect on a contact mechanism. For example, in the trigger switch, there is a risk that rainwater invades during work to generate a short circuit. In order to prevent the adverse effect, there is also made a proposal that bonding surfaces of covers constituting a housing are sealed by ultrasonic welding to enhance a water-resistant property and a dust-resistant property.
However, when the bonding surfaces of the covers are sealed by the ultrasonic welding, internal air hardly flows to the outside, and air resistance is increased when the trigger is depressed, which results in a strange manipulation feeling.